This invention relates to a hand-held milling machine for the processing of workpieces and especially for the trimming of workpiece edges and, incorporating at least one power-driven rotary milling tool, a machine support plate relative to which the milling tool protrudes on the side facing the workpiece and by which the hand-held milling machine can rest on the workpiece. A screw-type clamping mechanism having one clamping section is respectively associated with the milling tool and the support plate, and it features at least one actuating element. The milling tool and the support plate move relative to each other through relative rotational movement of the clamping sections on either side around a drive spindle axis in the direction in which the milling tool protrudes relative to the support plate. The clamping sections on either side are located opposite each other in a radial direction relative to the drive spindle axis. A releasable tensioning device tightens the clamps in the radial direction of the drive spindle axis and the radially inward (inner) clamping section can be brought into contact with the radially outward (outer) clamping section, allowing the two clamping sections on either side to be secured against any relative rotational movement around the drive spindle axis.
The screw-type clamping mechanism serves to define the depth of penetration of the milling tool in the workpiece being processed. In the case of edge cutting machines that are used for chamfering workpiece edges and therefore employ cutting tools whose cutting edges are angled relative to the tool drive axis, the degree of the chamfer on the workpiece edge varies as a function of the depth of penetration of the milling tool.
A hand-held milling machine of this general type has been described in U.S. Pat. No. 1,514,894. In the prior art design, a milling tool is positioned on a motor housing that doubles as part of a screw-type clamping mechanism and is therefore provided with an outside thread. That outside thread on the motor housing engages with a female (i.e., inside) thread on a hollow cylindrical machine support. Relative rotational movement of the motor housing and the machine support permits the variation of the projection of the milling tool on the workpiece side relative to the machine support and thus the depth of penetration of the milling tool on the workpiece being processed. For locking the components in a selected setting, the wall of the hollow cylindrical machine support is slotted in the axial direction of the hollow cylinder and provided on both sides of the slot with radially protruding flanges. A clamping screw extends through both flanges.
Tightening the clamping screw by turning it causes the flanges and thus the edges of the slot on the machine support to be drawn together to a point where the inside thread of the machine support and the outside thread of the motor housing are frictionally engaged, essentially blocking any unintentional rotational movement of the machine support relative to the motor housing. The friction lock between the motor housing and the machine support is released by loosening the clamping screw and turning it in the opposite direction. In the process the hollow cylindrical machine support expands to a degree. If the clamping screw is loosened too much, causing a correspondingly excessive spreading of the machine support, the result may be an unintentional disengagement of the inside thread of the machine support from the outside thread of the motor housing.
It is an object of this invention to provide a novel hand-held milling machine which provides improved functional reliability.
Another object is to provide such a milling machine which is readily manipulatable.
It has now been found that the foregoing and related objects may be readily attained in a hand-held milling machine for the processing of workpieces and especially for the trimming of workpiece edges including at least one power driven rotary cutting tool and a machine support relative to which the cutting tool protrudes on the side facing an associated workpiece. The support serves to support the hand-held milling machine on the associated workpiece being processed. A screw-type clamping mechanism having one clamping section associated with the cutting tool and the machine support has at least one actuating element serving to move the cutting tool and the machine support relative to each other through relative rotary movement of the clamping sections on each side around a drive spindle axis, in the direction of projection of the cutting tool relative to the machine support. The clamping sections on the two sides being positioned opposite each other in a radial direction relative to the drive axis
A releasable tensioning device acts in a radial direction relative to the drive axis whereby the radially inward (inner) clamping section can be brought into contact with the radially outward clamping section, allowing the two clamping sections on both sides to be secured against any relative rotational movement around the drive axis. The tensioning device includes an annular tensioning element that is at least in part radially positioned outside the outer clamping section. An actuating device is operable to tighten and loosen the tensioning element in the circumferential directions, whereby tightening of the tensioning element can bring the outer clamping section into contact with the inner clamping section.
Desirably, the tensioning element is in the form of a smooth walled tensioning ring, tensioning strap or similar element, and the actuating device employed is a manual actuating lever. The tensioning element is mounted directly on the outer clamping section and the outer clamping section is provided with at least one recessed seat for receiving the tensioning element.
Preferably, the clamping section associated with the cutting tool constitutes the inner clamping section on a machine base unit and the clamping section associated with the machine support constitutes the outer clamping section. When the tensioning device is in the unclamped state, the tensioning element and/or the actuating device is/are rotationally locked on the machine base unit in the direction of relative rotational movement of the clamping sections on the two sides while the tensioning element and the outer clamping section can be rotated relative to each other in the direction of the relative rotational movement.
The tensioning element can be tensioned by radially protruding clamping flanges which are positioned opposite each other in the circumferential direction with a gap between them, and an anti-rotation lock is provided on the machine base unit for the tensioning element and/or the actuating device, the anti-rotation lock engaging in the gap between the clamping flanges.
Desirably, the anti-rotation lock for the annular tensioning element is in the form of an anti-rotation lock pin.
As can be seen, the milling machine of the present invention enables the clamping sections of the screw-type clamping mechanism and the tensioning device to be physically separated. Accordingly, the clamping sections and the tensioning device can be operated and manipulated without necessarily affecting the respective other component of the hand-held milling machine.
The machine has a simple tensioning device and the functional reliability of the tensioning device is assured by locating the tensioning element on the outer clamping section.
The preferred design version of the machine provides for mutual physical association between the base unit of the machine and the clamping element, i.e., the actuating element of the tensioning device which is independent of the rotational position of the clamping section associated with the machine support plate relative to the clamping section that is associated with the milling tool. Consequently, regardless of the mutual setting between the milling tool and the machine support plate, the tensioning device can occupy a position that ensures its functional reliability and/or user-friendly operation.
The machine provides anti-rotation locking devices for the clamping element, i.e., actuating element of the tensioning device that can be implemented on hand-held milling machines.